A bipolar transistor capable of operating at high speeds. In a bipolar transistor designed for operation at high speeds, a polycrystalline silicon layer used as a base electrode effects is a contact area with respect to the base region which lacks precision or tends to increase. Further, when the transistor is formed in a small size, the ratio of the contact area with respect to the polycrystalline area increases, making it difficult to increase the operation speed. In order to reduce the contact area of the polycrystalline silicon layer, this invention deals with the structure in which the polycrystalline silicon layer is brought into contact with a portion near the edge of the convex semiconductor layer maintaining a small size and a high precision.